A hybrid vehicle may include a driveline disconnect clutch for coupling and decoupling an engine to a driveline that supplies torque to vehicle wheels. The driveline disconnect clutch may be opened to allow the engine to stop while the driveline rotates via torque provided by an electric machine. Stopping the engine may allow the vehicle to conserve fuel. The driveline disconnect clutch may be closed when a driver torque demand exceeds a threshold torque. By closing the driveline disconnect clutch, engine torque may be provided to the driveline. However, adjusting the driveline disconnect clutch state simply based upon a driver torque demand may cause the driveline to limit launching of the vehicle solely via the electric machine, thereby degrading vehicle fuel economy.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating a hybrid vehicle, comprising: adjusting operation of a driveline disconnect clutch in response to a change in vehicle mass.
By adjusting operation of a driveline disconnect clutch in response to changes in vehicle mass, it may be possible to allow a vehicle to continue to launch via an electric machine even though a driver demand torque has increased in response to an increase in vehicle mass. For example, a vehicle may be allowed to creep at low vehicle speeds (e.g., 0-5 MPH) even as vehicle mass increases by holding a driveline disconnect clutch in an open state until an increased driver demand torque is requested. In this way, a vehicle may continue to operate in a similar manner at lower and higher vehicle masses.
The present description may provide several advantages. Specifically, the approach may reduce a number of driveline disconnect clutch opening and closing events so that driveline torque disturbances may be reduced. Further, the approach may improve vehicle drivability. Further still, the approach may reduce driveline wear, thereby increasing the operating life of the driveline.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.